Magneto-resistive effect element and magnetic memory

ABSTRACT

It is possible to obtain excellent heat stability even though the element is miniaturized and keep stable magnetic domains even though switching is repeated any number of times. A magneto-resistive effect element includes: a magnetization-pinned layer including a magnetic film having a spin moment oriented in a direction perpendicular to a film surface thereof and pinned in the direction; a magnetic recording layer having a spin moment oriented in a direction perpendicular to a film surface thereof; a nonmagnetic layer formed between the magnetization-pinned layer and the magnetic recording layer; and an anti-ferromagnetic film formed on at least side surfaces of the magnetization-pinned layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2003-194513, filed on Jul. 9, 2003in Japan, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magneto-resistive effect element anda magnetic memory.

2. Related Art

A magneto-resistive effect element having magnetic films is used for amagnetic head, a magnetic sensor and so forth, and it has been proposedto be used for a solid magnetic memory. In particular, there is anincreasing interest in a magnetic random access memory (hereinafter,referred to as “MRAM (Magnetic Random Access Memory)), which utilizesthe magneto-resistive effect of ferromagnetic material, as a nextgeneration solid non-volatile memory capable of carrying out a rapidreading/writing and an operation with large capacity and low powerconsumption.

In recent years, a ferromagnetic tunnel junction element or theso-called “tunneling magneto-resistive element (TMR element)” has beenproposed as a magneto-resistive effect element utilizing a tunnelcurrent and having a sandwiching structure where one dielectric isinserted between two ferromagnetic metal layers, and a current is causedto flow perpendicular to a film face to utilize a tunneling current. Inthe tunneling magneto-resistive element, since a magneto-resistancechange ratio (MR ratio) has reached 20% or more, a possibility of theMRAM to public application is increasing.

The TMR element is realized by the following method. That is, after athin AL (aluminum) layer having a thickness of 0.6 nm to 2.0 nm isformed on a ferromagnetic electrode, and the surface of the Al layer isexposed to oxygen glow discharge or an oxygen gas to form a tunnelbarrier layer consisting of Al₂O₃.

Further, a ferromagnetic single tunnel junction having a structure wherea magnetization direction of one of ferromagnetic layers constitutingthe ferromagnetic single tunnel junction is pinned by ananti-ferromagnetic layer has been proposed.

Further a ferromagnetic tunnel junction obtained through magneticparticles diffused in a dielectric material and a ferromagnetic dualtunnel junction have been also proposed.

In view of the fact that a magneto-resistance change ratio in a range of20% to 50% have been also achieved in these tunneling magneto-resistiveelements and the fact that reduction in magneto-resistance change ratiocan be suppressed even if a voltage value to be applied to a tunnelingmagneto-resistive element is increased in order to obtain a desiredoutput voltage value, there is a possibility of the TMR element toapplication to the MRAM.

When the TMR element is used in the MRAM, one of the two ferromagneticlayers interposing the tunnel barrier layer, i.e., amagnetization-pinned layer whose magnetization direction is pinned so asto not change is defined as a magnetization reference layer, and theother thereof, i.e., a magnetization free layer whose magnetizationdirection is easily allowed to be inverted is defined as a storagelayer. A state in which the magnetization directions in the referencelayer and the storage layer are parallel to each other and a state inwhich the directions are antiparallel to each other are assigned topieces of binary information “0” and “1”, respectively, so thatinformation can be stored.

Recording information is written by inverting the magnetizationdirection in the storage layer by an induced magnetic field generated byflowing a current in a write wiring arranged near the TMR element. Therecording information is read by detecting a change in resistance causedby a TMR effect.

A magnetic recording element using the ferromagnetic single tunneljunction or the ferromagnetic dual tunnel junction is nonvolatile andhas a short write/read time of 10 ns or less and potential, i.e., can berewritten 10¹⁵ or more. In particular, in a magnetic recording elementusing a ferromagnetic dual tunnel junction, as described above, adecrease in magneto-resistance change ratio can be suppressed eventhough a voltage applied to the ferromagnetic tunnel junction element isincreased to obtain a desired large output voltage, and preferablecharacteristic for a magnetic recording element can be achieved.

However, regarding a cell size of the memory, when an architecture wherea cell is constituted by one transistor and one TMR element is used, itis disadvantageously impossible to make a memory cell size smaller thanthe size of a semiconductor DRAM (Dynamic Random Access Memory).

In order to solve the above problem, a diode architecture in which a TMRelement and a diode are serially connected between a bit line and a wordline and a simple matrix architecture in which a TMR element is arrangedbetween a bit line and a word line are proposed.

However, when a design rule is set at 0.18 μm or less, the followingproblem is posed. That is, a magnetic material cannot keep heatstability due to the influence of heat disturbances to make impossibleto keep nonvolatile properties. In addition, when magnetizationswitching of the magnetization free layer is repeated several times inthe TMR element having a design rule of 0.18 μm or more, themagnetization free layer has a plurality of magnetic domains. Bits ofthe plurality of magnetic domains have extremely poor thermal stability.

In order to solve these problems, it is proposed that a plurality ofmagnetization free layers are provided in a magneto-resistive effectelement or a perpendicular-magnetization material is used in as thematerial of the magneto-resistive effect element.

When a magneto-resistive effect element (for example, see thespecification of U.S. Pat. No. 5,953,248) having a plurality ofmagnetization free layers is used, the heat stability of themagnetization free layers is kept until the design rule is about 0.09μm. However, the magneto-resistive effect element is miniaturized tohave a design rule smaller than 0.09 μm, the problem of heatdisturbances also becomes conspicuous.

When the perpendicular-magnetization material is used (for example, seeJapanese Patent Laid-Open Publication No. 11-213650), the volumes of themagnetization free layer and the magnetization-pinned layer can beincreased in the direction of perpendicular magnetization. For thisreason, the problems of heat stability and heat disturbances can besolved. Further miniaturizing can be achieved.

However, when a perpendicular-magnetization material is used as amagnetic material, a magneto-resistive effect element that can achieve apreferable exchange coupling between anti-ferromagnetic layer andferromagnetic layer is unknown up to now.

When a parallel-magnetization material is used as a magnetic material, aTMR element that can achieve a preferable magnetic coupling betweenanti-ferromagnetic layer and ferromagnetic layer is known. For example,in a TMR element that includes an underlying electrode, ananti-ferromagnetic layer, a magnetization-pinned layer having aferromagnetic layer, a tunnel barrier layer, a magnetization free layerand a cap layer, and in that the magnetization-pinned layer and themagnetization free layer have in-plane magnetizations, respectively, alaminated structure constituted by the magnetization-pinned layer havingthe ferromagnetic layer and the anti-ferromagnetic layer is used. Forthis reason, a preferable exchange coupling between theanti-ferromagnetic layer and the ferromagnetic layer can be achieved.

However, even though the laminated structure constituted by themagnetization-pinned layer having the ferromagnetic layer and theanti-ferromagnetic layer is simply applied to the TMR element made of amaterial which is shown in Japanese Patent Laid-Open Publication No.11-213650 and which can be perpendicularly magnetized, a preferableexchange coupling between the anti-ferromagnetic layer and theferromagnetic layer cannot be achieved.

For this reason, even though a perpendicular magnetization material suchas a Co—Cr—Pt alloy having high coercive force is used as themagnetization material of the magnetization-pinned layer, when switchingof the magnetization of the magnetization free layer is repeated, themagnetization of the magnetization-pinned layer vary due to theinfluence of a leakage magnetic field of the magnetization free layerand an Orange Peal coupling to form a plurality of magnetic domains. Asa result, a magneto-resistance change ratio decreases.

As described above, a magneto-resistive effect element that hasexcellent heat stability even though the element is miniaturized andthat can keep stable magnetic domains even though switching is repeatedany number of times must be realized.

SUMMARY OF THE INVENTION

The present invention has been made on the basis of recognition of theabove problems, and has as its object to provide a magneto-resistiveeffect element that has excellent heat stability even though the elementis miniaturized and that can keep stable magnetic domains even thoughswitching is repeated any number of times, and a magnetic memory havingthe magneto-resistive effect element in a memory cell.

A magneto-resistive effect element according to a first aspect of thepresent invention includes: a magnetization-pinned layer including amagnetic film having a spin moment oriented in a direction perpendicularto a film surface thereof and pinned in the direction; a magneticrecording layer having a spin moment oriented in a directionperpendicular to a film surface thereof; a nonmagnetic layer formedbetween the magnetization-pinned layer and the magnetic recording layer;and an anti-ferromagnetic film formed on at least side surfaces of themagnetization-pinned layer.

A magnetic memory according to a second aspect of the present inventionincludes at least a memory cell, the memory cell including amagneto-resistive effect element as a memory element, themagneto-resistive effect element includes: a magnetization-pinned layercomprising a magnetic film having a spin moment oriented in a directionperpendicular to a film surface thereof and pinned in the direction; amagnetic recording layer having a spin moment oriented in a directionperpendicular to a film surface thereof; a nonmagnetic layer formedbetween the magnetization-pinned layer and the magnetic recording layer;and an anti-ferromagnetic film formed on at least the side surfaces ofthe magnetization-pinned layer.

A magnetic memory according to a third aspect of the present inventionincludes: a first wiring; a second wiring crossing the first wiring; anda magneto-resistive effect element arranged in a crossing area betweenthe first wiring and the second wiring, having one end electricallyconnected to the first wiring, and including a magnetization-pinnedlayer comprising a magnetic film having a spin moment oriented in adirection perpendicular to a film surface thereof and pinned in thedirection; a magnetic recording layer having a spin moment oriented in adirection perpendicular to a film surface thereof; a nonmagnetic layerformed between the magnetization-pinned layer and the magnetic recordinglayer; and an anti-ferromagnetic film formed on at least the sidesurfaces of the magnetization-pinned layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a second embodiment of the presentinvention.

FIG. 3 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a fourth embodiment of the presentinvention.

FIG. 5 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a seventh embodiment of the presentinvention.

FIG. 8 is a sectional view showing a constitution of a magneto-resistiveeffect element according to a eighth embodiment of the presentinvention.

FIG. 9 is a sectional view showing a constitution of a first concreteexample of a memory structure used in a magnetic memory according to thepresent invention.

FIG. 10 is a sectional view showing a constitution of a second concreteexample of the memory structure used in the magnetic memory according tothe present invention.

FIG. 11 is a sectional view showing a constitution of a third concreteexample of the memory structure used in the magnetic memory according tothe present invention.

FIG. 12 is a sectional view showing a constitution of a fourth concreteexample of the memory structure used in the magnetic memory according tothe present invention.

FIG. 13 is a sectional view showing a constitution of a magnetic memoryaccording to a ninth embodiment of the present invention.

FIG. 14 is a sectional view showing a constitution of a magnetic memoryaccording to a modification of the ninth embodiment of the presentinvention.

FIG. 15 is a sectional view showing a manufacturing step of a method ofmanufacturing a magnetic memory according to a tenth embodiment of thepresent invention.

FIG. 16 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 17 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 18 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 19 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 20 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 21 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 22 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 23 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 24 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 25 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 26 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 27 is a sectional view showing a manufacturing step of the methodof manufacturing the magnetic memory according to the tenth embodimentof the present invention.

FIG. 28 is a graph showing the rewritable count tolerances of a magneticmemory manufactured by the manufacturing method according to the tenthembodiment of the present invention and a comparative example.

FIG. 29 is a graph showing the rewritable count tolerances of a magneticmemory according to an eleventh embodiment of the present invention anda comparative example and a comparative example.

FIG. 30 is a sectional view showing a constitution of a magnetic memoryaccording to a twelfth embodiment of the present invention.

FIG. 31 is a graph showing a measurement result of writing by spininjection in the magnetic memory according to a twelfth embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below withreference to the accompanying drawings.

First Embodiment

A constitution of a magneto-resistive effect element according to afirst embodiment of the present invention is shown in FIG. 1. Themagneto-resistive effect element 2 according to this embodiment is a TMRelement, and comprises a magnetization-pinned layer (to be also referredto as a pinned layer hereinafter) 4 having a perpendicular spin moment,a magnetization free layer (to be also referred to as a free layerhereinafter) 8 having a perpendicular spin moment and serving as amagnetic recording layer, a tunnel barrier layer 6 provided between themagnetization-pinned layer 4 and the magnetization free layer 8, and ananti-ferromagnetic film 9 covering side surfaces of themagnetization-pinned layer 4 and a surface of the magnetization-pinnedlayer 4 opposing the tunnel barrier layer 6.

In this manner, in the magneto-resistive effect element according to theembodiment, the anti-ferromagnetic film 9 is formed on at least sidesurfaces of the magnetization-pinned layer 4. Therefore, even though themagneto-resistive effect element is miniaturized, the direction of thespin moment of the magnetization-pinned layer 4 is perpendicularlyoriented by an exchange coupling between the magnetization-pinned layer4 and the anti-ferromagnetic film 9. Even though switching of magneticfields is repeated, the magnetization direction of themagnetization-pinned layer 4 does not vary. Therefore, the magnetizationof the magnetization-pinned layer 4 can be kept stable without becominga plurality of magnetic domains, and the magneto-resistance change ratiocan be prevented from being reduced.

Second Embodiment

A constitution of a magneto-resistive effect element according to asecond embodiment of the present invention is shown in FIG. 2. Themagneto-resistive effect element 2 according to the embodiment has aconstitution obtained by removing the anti-ferromagnetic film 9 on thesurface of the magnetization-pinned layer 4 opposing the tunnel barrierlayer 6 from the magneto-resistive effect element 2 according to thefirst embodiment shown in FIG. 1, i.e., forming the anti-ferromagneticfilm 9 only on the side surfaces of the magnetization-pinned layer 4.

For this reason, even though the magneto-resistive effect element isminiaturized, the spin moment direction of the magnetization-pinnedlayer 4 is perpendicularly oriented by exchange coupling between theanti-ferromagnetic film 9 and the magnetization-pinned layer 4. Eventhough switching of the magnetic fields is repeated, the magnetic domainof the magnetization-pinned layer 4 does not vary. Therefore, themagnetization of the magnetization-pinned layer 4 can be kept stablewithout becoming a plurality of magnetic domains, and themagneto-resistance change ratio can be prevented from being reduced.

Third Embodiment

A constitution of a magneto-resistive effect element according to athird embodiment of the present invention is shown in FIG. 3. Themagneto-resistive effect element 2 according to the embodiment has aconstitution obtained by forming a nonmagnetic conductive layer 5 on theupper surface of the magnetization-pinned layer 4 in themagneto-resistive effect element 2 according to the first embodimentshown in FIG. 1.

In the magneto-resistive effect element according to the embodiment, theanti-ferromagnetic film 9 is formed on at least side surfaces of themagnetization-pinned layer 4. Therefore, the spin moment of themagnetization-pinned layer 4 is perpendicularly oriented by exchangecoupling between the magnetization-pinned layer 4 and theanti-ferromagnetic film 9 even though the magneto-resistive effectelement is miniaturized, and the magnetization of themagnetization-pinned layer 4 does not vary even though switching of themagnetic fields is repeated. Therefore, the magnetization of themagnetization-pinned layer 4 can be kept stable without becoming aplurality of magnetic domains, and the magneto-resistance change ratiocan be prevented from being reduced.

When the magneto-resistive effect element according to the thirdembodiment is used as a memory element of a magnetic memory, thenonmagnetic conductive layer 5 can be used as a bit line.

Fourth Embodiment

A constitution of a magneto-resistive effect element according to afourth embodiment of the present invention is shown in FIG. 4. Themagneto-resistive effect element 2 according to the embodiment has aconstitution obtained by forming a nonmagnetic conductive layer 5 on theupper surface of the magnetization-pinned layer 4 in themagneto-resistive effect element 2 according to the second embodimentshown in FIG. 2.

In the magneto-resistive effect element according to the embodiment, theanti-ferromagnetic film 9 is formed on side surfaces of themagnetization-pinned layer 4. In this manner, the spin moment of themagnetization-pinned layer 4 is perpendicularly oriented by exchangecoupling between the magnetization-pinned layer 4 and theanti-ferromagnetic film 9 even though the magneto-resistive effectelement is miniaturized, and the magnetization of themagnetization-pinned layer 4 does not vary even though switching of themagnetic fields is repeated. Therefore, the magnetization of themagnetization-pinned layer 4 can be kept stable without becoming aplurality of magnetic domains, and the magneto-resistance change ratiocan be prevented from being reduced.

When the magneto-resistive effect element according to the fourthembodiment is used as a memory element of a magnetic memory, thenonmagnetic conductive layer 5 can be used as a bit line.

Fifth Embodiment

A constitution of a magneto-resistive effect element according to afifth embodiment of the present invention is shown in FIG. 5. Themagneto-resistive effect element 2 according to the embodiment uses atop-pin type tunnel single junction, and has a magnetization-pinnedlayer 4 having a laminated structure constituted by a perpendicularmagnetic layer 4 a, a nonmagnetic conductive layer 4 b, and a hard biaslayer (bias-applied magnetic layer) 4 c in the magneto-resistive effectelement 2 according to the first embodiment shown in FIG. 1. Morespecifically, the hard bias layer 4 c is formed on the perpendicularmagnetic layer 4 a through the nonmagnetic conductive layer 4 b. As inthe embodiment, the bias-applied magnetic layer 4 c is formed to make itpossible to reduce a demagnetizing field, and more stablecharacteristics can be obtained. Therefore, a reliable magneto-resistiveeffect element can be obtained.

In the magneto-resistive effect element according to this embodiment,the anti-ferromagnetic film 9 is also formed on at least side surfacesof the magnetization-pinned layer 4. Therefore, the spin moment of themagnetization-pinned layer 4 is perpendicularly oriented by exchangecoupling between the magnetization-pinned layer 4 and theanti-ferromagnetic film 9 even though the magneto-resistive effectelement is miniaturized, and the magnetization of themagnetization-pinned layer 4 does not vary even though switching of themagnetic fields is repeated. Therefore, the magnetization of themagnetization-pinned layer 4 can be kept stable without becoming aplurality of magnetic domains, and the magneto-resistance change ratiocan be prevented from being reduced.

Sixth Embodiment

A constitution of a magneto-resistive effect element according to thesixth embodiment of the present invention is shown in FIG. 6. Themagneto-resistive effect element 2 according to the embodiment is atop-pin type tunnel single junction, and has a magnetization-pinnedlayer 4 having a laminated structure constituted by a perpendicularmagnetic layer 4 a, a nonmagnetic conductive layer 4 b, and a hard biaslayer (bias-applied magnetic layer) 4 c in the magneto-resistive effectelement 2 according to the first embodiment shown in FIG. 2. Morespecifically, the hard bias layer 4 c is formed on the perpendicularmagnetic layer 4 a through the nonmagnetic conductive layer 4 b. As inthis embodiment, the bias-applied magnetic layer is formed to make itpossible to reduce a demagnetizing field, and more stablecharacteristics can be obtained. Therefore, a reliable magneto-resistiveeffect element can be obtained.

In the magneto-resistive effect element according to the embodiment, theanti-ferromagnetic film 9 is also formed on at least side surfaces ofthe magnetization-pinned layer 4. Therefore, the spin moment of themagnetization-pinned layer 4 is perpendicularly oriented by exchangecoupling between the magnetization-pinned layer 4 and theanti-ferromagnetic film 9 even though the magneto-resistive effectelement is miniaturized, and the magnetization of themagnetization-pinned layer 4 does not vary even though switching of themagnetic fields is repeated. Therefore, the magnetization of themagnetization-pinned layer 4 can be kept stable without becoming aplurality of magnetic domains, and the magneto-resistance change ratiocan be prevented from being reduced.

Seventh Embodiment

A constitution of a magneto-resistive effect element according to aseventh embodiment of the present invention is shown in FIG. 7. Themagneto-resistive effect element 2 according to the embodiment uses abottom-pin type tunnel single junction, and has a configuration obtainedby turning the magneto-resistive effect element 2 according to the fifthembodiment shown in FIG. 5 upside down. More specifically, themagnetization-pinned layer 4 has a laminated structure constituted by ahard bias layer (bias-applied magnetic layer) 4 c, a nonmagneticconductive layer 4 b, and a perpendicular magnetic layer 4 a. In theconfiguration, a tunnel barrier layer 6 is formed on the perpendicularmagnetic layer 4 a, a magnetization free layer 8 is formed on the tunnelbarrier layer 6, and a anti-ferromagnetic film 9 is formed on sidesurfaces of the magnetization-pinned layer 4 and the bottom surface (thebottom surface of the hard bias layer 4 c) of the magnetization-pinnedlayer 4.

As in this embodiment, the bias-applied magnetic layer is formed to makeit possible to reduce a demagnetizing field, and more stablecharacteristics can be obtained. Therefore, a reliable magneto-resistiveeffect element can be obtained.

In the magneto-resistive effect element according to the embodiment, theanti-ferromagnetic film 9 is also formed on at least side surfaces ofthe magnetization-pinned layer 4. Therefore, the spin moment of themagnetization-pinned layer 4 is perpendicularly oriented by exchangecoupling between the magnetization-pinned layer 4 and theanti-ferromagnetic film 9 even though the magneto-resistive effectelement is miniaturized, and the magnetization of themagnetization-pinned layer 4 does not vary even though switching of themagnetic fields is repeated. Therefore, the magnetization of themagnetization-pinned layer 4 can be kept stable without becoming aplurality of magnetic domains, and the magneto-resistance change ratecan be prevented from being reduced.

The magneto-resistive effect elements according to the first to sixthembodiments use top-pin type tunnel single junctions. However, as in theseventh embodiment, the magneto-resistive effect element may use thebottom-pin type single junction.

Eighth Embodiment

A configuration of a magneto-resistive effect element according to theeighth embodiment of the present invention is shown in FIG. 8. Amagneto-resistive effect element 2A uses dual tunnel junctions, and hasa configuration in which the magnetization free layer 8 of themagneto-resistive effect element according to the fifth embodiment shownin FIG. 5 and the magnetization free layer 8 of the magneto-resistiveeffect element according to the seventh embodiment shown in FIG. 7 areshared. More specifically, a magnetization-pinned layer 4 ₂ has alaminated structure constituted by a hard bias layer (bias-appliedmagnetic layer) 4 c ₂, a nonmagnetic conductive layer 4 b ₂, and aperpendicular magnetic layer 4 a ₂. A tunnel barrier layer 6 ₂ is formedon the perpendicular magnetic layer 4 a ₂, a magnetization free layer 8is formed on the tunnel barrier layer 6 ₂, and a tunnel barrier layer 6₁ is formed on the magnetization free layer 8. A magnetization-pinnedlayer 4 ₁ having a laminated structure constituted by a perpendicularmagnetic layer 4 a ₁, a nonmagnetic conductive layer 4 b ₁, and a hardbias layer 4 c ₁ is formed on the tunnel barrier layer 6 ₁. The sidesurfaces and the upper surface of the magnetization-pinned layer 4 ₁ arecovered with an anti-ferromagnetic film 9 ₁, and the side surfaces andthe bottom surface of the magnetization-pinned layer 4 ₂ are coveredwith a anti-ferromagnetic film 9 ₂.

Even in this embodiment, at least the side surfaces of themagnetization-pinned layer 4 ₁ is covered with the anti-ferromagneticfilm 9 ₁, and at least the side surfaces of the magnetization-pinnedlayer 4 ₂ is covered with the anti-ferromagnetic film 9 ₂. In thismanner, the spin moments of the magnetization-pinned layers 4 ₁ and 4 ₂are perpendicularly oriented by exchange coupling between themagnetization-pinned layers 4 ₁, 4 ₂ and the anti-ferromagnetic films 9₁, 9 ₂ even though the magneto-resistive effect element is miniaturized,and the magnetizations of the magnetization-pinned layers 4 ₁ and 4 ₂ donot vary even though switching of the magnetic fields is repeated.Therefore, each of the magnetizations of the magnetization-pinned layer4 ₁ and 4 ₂ can be kept stable without becoming a plurality of magneticdomains, and the magneto-resistance change ratio can be prevented frombeing reduced.

In this embodiment, the dual tunnel junctions obtained such that themagnetization free layers of the magneto-resistive effect element usingthe top-pin type tunnel single junction according to the fifthembodiment and the magneto-resistive effect element using the bottom-pintype tunnel single junction according to the seventh embodiment areconnected to each other to share the magnetization free layers is used.However, the following configuration may be used. That is, any one ofthe top-pin type tunnel single junction magneto-resistive effectelements according to the first to fifth embodiments and a bottom-pintype magneto-resistive effect element formed on the basis of one of themagneto-resistive effect elements according to the first to fifthembodiments are connected such that the magnetization free layers areshared, thereby forming a dual tunnel junctions magneto-resistive effectelement.

In the magneto-resistive effect elements according to the first toeighth embodiments, even though a planar aspect ratio, i.e., a ratio ofthe minor axis to the major axis is 1.5 or less, a spin moment is stablypresent, thereby it is possible to reduce an area per bit. Therefore,the magneto-resistive effect elements according to the first to eighthembodiments are suitably used as memory elements of large-capacitynonvolatile memories, and have excellent heat stability. Themagneto-resistive effect element is formed on the basis of a design ruleof 0.1 μm or less, a spin magnetic moment is stably kept, and an MRAMhaving a capacity larger than 1 Gbit can be practically applied.

In the magneto-resistive effect elements according to theabove-mentioned embodiments, a ferromagnetic material which can be usedas a magnetization-pinned layer or a magnetic recording layer will bedescribed below.

As a magnetic material of a magnetization-pinned layer, Co, Fe, Ni, analloy thereof (Co—Fe alloy, Co—Ni alloy, Ni—Fe alloy, or a Co—Ni—Fealloy), Co—Cr—Pt—Ta, Co—Cr—Nb—Pt, Co—Cr—Pt, Co—Cr—Pt/Ti, Co—Pt—Cr—O,Co—Cr—Pt—SiO₂, Co—Cr—Pt—B , Fe—Pt, Tb—Fe—Co, Pr—Tb—Co, or the like canbe used. And as a magnetization-pinned layer, a multi-layered filmconsisting of Co—Cr—Ta/Co—Zr—Nb/Co—Sm, a multi-layered film obtained bylaminating layers consisting of Co—Cr—Ta and Pt, a multi-layered filmobtained by laminating layers consisting of Co and Pd, a multi-layeredfilm obtained by laminating layers consisting of Co—B and Pd, or thelike can be used. Symbols “X-Y” denote contained components X and Y, anda symbol “/” denotes a laminated structure.

As a magnetic material of a magnetization free layer serving as amagnetic recording layer, Co—Cr—Pt—Ta, Co—Cr—Nb—Pt, Co—Cr—Pt,Co—Pt—Cr—O, Co—Cr—Pt—SiO₂, Co—Cr—Pt—B, Fe—Pt, Tb—Fe—Co, Pr—Tb—Co, or thelike can be used. And as a magnetization free layer serving as amagnetic recording layer, a multi-layered film consisting ofCo—Cr—Pt/Ti, or Co—Cr—Ta/Co—Zr—Nb/Co—Sm, a multi-layered film obtainedby laminating layers consisting of Co—Cr—Ta and Pt, a multi-layered filmobtained by laminating layers consisting of Co and Pd, a multi-layeredfilm obtained by laminating layers consisting of Co—B and Pd, or thelike can be used.

The magnetization-pinned layer consisting of one of these materials hasa unidirectoinal magnetic anisotropy by exchange coupling between themagnetization-pinned layer and the anti-ferromagnetic layer on the sidesurfaces. The magnetic recording layer (magnetization free layer)desirably has a uni-axial magnetic anisotropy in a directionperpendicular to the film surface. The thickness of the magneticrecording layer is not limited to a specific thickness. However, thethickness preferably falls within 1 nm to 100 nm. In addition, since thefilm thicknesses of the ferromagnetic layers constituting themagnetization-pinned layer and the magnetization free layer havemagnetic anisotropy in the perpendicular direction, the film thicknessescan be increased. A magneto-resistive effect element having a toleranceto thermal fluctuation can be obtained even though the magneto-resistiveeffect element is miniaturized.

Further, it is preferable that magnetization of a ferromagnetic layerused as the magnetization-pinned layer is fixed by providing ananti-ferromagnetic film to the magnetization-pinned layer. Such ananti-ferromagnetic film can comprise Fe (iron)-Mn (manganese), Pt(platinum-Mn (magnanese), Pt (platinum)-Cr (chromium)-Mn (manganese), Ni(nickel)-Mn (manganese), Ir (iridium)-Mn (manganese), NiO (nickeloxide), Fe₂O₃ (iron oxide) or the like.

Furthermore, the magnetic characteristic of magnetic material used maybe adjusted by adding thereto nonmagnetic element such as Ag (silver),Cu (copper), Au (gold), Al (aluminum), Mg (magnesium), Si (silicone), Bi(bismuth), Ta (tantalum), B (boron), C (carbon), O (oxygen), N(nitrogen), Pd (palladium), Pt (platinum), Zr (zirconium), Ir (iridium),W (tungsten), Mo (molybdenum), Nb (niobium) or the like. Besides,various physical properties such as crystallization, mechanicalproperties, chemical properties or the like can be adjusted.Furthermore, some Fe (iron) may be added to a Co-based alloy used in themagnetic recording layer.

On the other hand, a stacked layer film comprising a ferromagnetic layerand a nonmagnetic layer may be used as the magnetization-pinned layer orthe magnetic recording layer. For example, a film having a three-layeredstructure including a ferromagnetic layer/a nonmagnetic layer/aferromagnetic layer or a multi-layered film with three or more layersmay be used. In this case, it is preferable that an anti-ferromagneticinteraction acts to the ferromagnetic layers sandwiching the nonmagneticlayer.

The nonmagnetic material is not limited to a specific nonmagneticmaterial. However, as nonmagnetic material, for example, Ru (ruthenium),Ir (iridium), Os (osmium), Re (Rhenium), Cu (copper), Ag (silver), Au(gold), Ta (tantalum), W (tungsten), Si (silicon), Bi (bismuth), B(boron), C (carbon), Pd (palladium), Pt (platinum), Zr (zirconium), Nb(niobium), V (vanadium), Mo (molybdenum), an alloy thereof, or the likecan be used. When this structure is used, a demagnetizing field can bereduced by a biased magnetic field, and the magnetization of themagnetization-pinned layer is easily affected by the influence of amagnetic field induced by flowing a current to a bit line or a wordline, thereby the magnetization can be firmly pinned. The film thicknessof the nonmagnetic layer must be set to prevent super paramagnetism frombeing generated, and more desirably set at 0.4 nm or more and 10 nm orless.

Even in the magnetic recording layer, a nonmagnetic element such as Ag(silver), Cu (copper), Au (gold), Al (aluminum), Ru (ruthenium), Os(osmium), Re (rhenium), Mg (magnesium), Si (silicon), Bi (bismuth), Ta(tantalum), B (boron), C (carbon), O (oxygen), N (nitrogen), Pd(palladium), Pt (platinum), Zr (zirconium), Ir (iridium), W (tungsten),Mo (molybdenum), Nb (niobium), or the like is added to the magneticmaterial to make it possible to control magnetic characteristics. Inaddition, various physicalities such as crystallinity, mechanicalcharacteristics, chemical characteristics can be controlled.

On the other hand, when a TMR element is used as a magneto-resistiveeffect element, as an insulating layer (or a dielectric layer) formedbetween a magnetization-pinned layer and a magnetic recording layer,Al₂O₃ (aluminum oxide), SiO₂ (silicon oxide), MgO (magnesium oxide), AlN(aluminum nitride), Bi₂O₃ (bismuth oxide), MgF₂ (magnesium fluoride),CaF₂ (calcium fluoride), SrTiO₂ (strontium titanium dioxide), AlLaO₃(aluminum lanthanum trioxide), Al—N—O (aluminum oxynitride), or the likecan be used.

These compounds need not have a perfectly precise stoichiometriccomposition. Oxygen, nitrogen, fluorine, or the like may be lacked, ormay be over or short. In addition, it is desired that the thickness ofthe insulating layer (dielectric layer) is so small that a tunnelcurrent flows in the insulating layer. Actually, the thickness isdesirably 10 nm or less.

The magneto-resistive effect element can be formed on a predeterminedsubstrate by using a conventional thin-film forming means such asvarious sputtering methods, a deposition method, or molecular beamepitaxy. As a substrate used in this case, for example, varioussubstrates such as Si (silicon), SiO₂ (silicon oxide), Al₂O₃ (aluminumoxide), spinel, and AlN (aluminum nitride) can be used.

On the substrate, as an underlying layer, a protective layer, or a hardmask, a specific layer is not formed. However, a layer consisting of Ta(tantalum) Ti (titanium), Pt (platinum), Pd (palladium), Au (gold), Ti(titanium)/Pt (platinum), Ta (tantalum)/Pt (platinum), Ti (titanium)/Pd(palladium), Ta (tantalum)/Pd (palladium), Cu (copper), Al (aluminum)-Cu(copper), Ru (ruthenium), Ir (iridium), Os (osmium), or the like may beformed.

Ninth Embodiment

Before the explanation of a magnetic memory according to a ninthembodiment of the present invention, a memory cell structure used in themagnetic memory according to the present invention will be describedbelow.

First Concrete Example

The first concrete example of a memory cell 3 having a simple matrixarchitecture structure which uses a MOS transistor on only theperipheral portion of a memory array and which does not use selectivetransistors bit by bit is shown in FIG. 9. The memory cell 3 accordingto the concrete example comprises a magneto-resistive effect element 2according to the third embodiment, an underlying layer 10 formed on thelower surface of a magnetization free layer 8 of the magneto-resistiveeffect element 2, a bit line 20 electrically connected to the underlyinglayer 10, a pair of word lines 30 ₁ and 30 ₂ formed on the side of themagnetization free layer through an insulating film, and a conductivelayer 5 formed on the magnetization-pinned layer 4 of themagneto-resistive effect element 2 also serves as a bit line. A magneticcovering film 25 is formed on the bit line 20, and magnetic coveringfilms 35 ₁ and 35 ₂ are formed on the word lines 30 ₁ and 30 ₂,respectively.

In the first concrete example, data is read by turning on a MOStransistor connected to the bit lines 20 and 5 to flow a sense currentin the magneto-resistive effect element 2. Data is written by usingorthogonal bit lines 20 and the pair of word lines 30 ₁ and 30 ₂.Opposite current pulses are applied to the two word lines 30 ₁ and 30 ₂,respectively. At this time, the end portions of the two word lines 30 ₁and 30 ₂ are electrically connected to the end portion of the memoryarray block to make it possible that the current pulses are applied tothe word lines 30 ₁ and 30 ₂ by one driver and one sinker, so thatmemory array efficiency can be improved. The magnetic covering films 25,35 ₁, and 35 ₂ are applied to the bit line 20 and the word lines 30 ₁and 30 ₂ which are used to write data. When the magnetic covering filmstructure is used, a current required to write data can be reduced, anddata can be written with a low power consumption and a small current.

The memory cell according to the first concrete example has an advantageover a memory cell according to the second concrete example with respectto the number of steps of etching, the number of masks, andmanufacturing cost.

Second Embodiment

A constitution of a second concrete example of a memory cell used in amagnetic memory according to the present invention is shown in FIG. 10.The memory cell 3 according to the concrete example has a simple matrixarchitecture structure which uses a MOS transistor on only theperipheral portion of a memory array and which does not use selectivetransistors bit by bit. The memory cell 3 comprises a magneto-resistiveeffect element 2 according to the first embodiment, an underlying layer10 formed on the lower surface of a magnetization free layer 8 of themagneto-resistive effect element 2, a bit line 20 electrically connectedto the underlying layer 10, a pair of word lines 30 ₁ and 30 ₂ formed onthe side of the magnetization free layer through an insulating film, aconductive layer 12 connected to the upper surface of themagneto-resistive effect element 2, and a bit line 22 electricallyconnected to the conductive layer 12. A magnetic covering film 25 isformed on the bit line 20, and magnetic covering films 35 ₁ and 35 ₂ areformed on the word lines 30 ₁ and 30 ₂, respectively.

In the second concrete example, data is read by turning on a MOStransistor connected to the bit line 20 and the bit line 22 to flow asense current in the magneto-resistive effect element 2. Data is writtenby using orthogonal bit lines 20 and the pair of word lines 30 ₁ and 30₂. Opposite current pulses are applied to the two word lines 30 ₁ and 30₂, respectively. At this time, the end portions of the two word lines 30₁ and 30 ₂ are electrically connected to the end portion of the memoryarray block to make it possible that the current pulses are applied tothe word lines 30 ₁ and 30 ₂ by one driver and one sinker, so thatmemory array efficiency can be improved. The magnetic covering films 25,35 ₁, and 35 ₂ are applied to the bit line 20 and the word lines 30 ₁and 30 ₂ which are used to write data. When the magnetic covering filmstructure is used, a current required to write data can be reduced, anddata can be written with a low power consumption and a small current.

Third Concrete Example

A constitution of a third concrete example of a memory cell used in amagnetic memory according to the present invention is shown in FIG. 11.The memory cell 3 according to the concrete example has a simple matrixarchitecture structure which uses a MOS transistor on only theperipheral portion of a memory array and which does not use selectivetransistors bit by bit. The memory cell 3 comprises a magneto-resistiveeffect element 2 according to the third embodiment, an underlying layer10 formed on the lower surface of a magnetization free layer 8 of themagneto-resistive effect element 2, a diode 15, a bit line 20electrically connected to the underlying layer 10 through the diode 15,and a pair of word lines 30 ₁ and 30 ₂ formed on the side of themagnetization free layer through an insulating film. A conductive layer5 formed on a magnetization-pinned layer 4 of the magneto-resistiveeffect element 2 also serves as a bit line. A magnetic covering film 25is formed on the bit line 20, and magnetic covering films 35 ₁ and 35 ₂are formed on the word lines 30 ₁ and 30 ₂, respectively.

In the third concrete example, data is read by turning on a MOStransistor connected to the bit line 20 and the bit line 5 to flow asense current in the magneto-resistive effect element 2. In a memorycell of a type which does not use a diode as in the first or secondconcrete example, in a read operation, a transistor connected to anotherbit line is opened, or the voltages of the bit line 20 and the bit line5 are made constant to reduce a current flowing around a non-selectedmagneto-resistive effect element as much as possible. However,disadvantageously, the current cannot be exactly zero. However, as inthe concrete example, the diode 15 is interposed between the underlyinglayer 10 and the bit line 20, so that the problem can be solved. As inthe second concrete example, data is written by using orthogonal bitlines 20 and the pair of word lines 30 ₁ and 30 ₂. Opposite currentpulses are applied to the two word lines 30 ₁ and 30 ₂, respectively. Atthis time, the end portions of the two word lines 30 ₁ and 30 ₂ areelectrically connected to the end portion of the memory array block tomake it possible that the current pulses are applied to the word lines30 ₁ and 30 ₂ by one driver and one sinker, so that memory arrayefficiency can be improved. The magnetic covering films 25, 35 ₁, and 35₂ are applied to the bit line 20 and the word lines 30 ₁ and 30 ₂ whichare used to write data as described above. When the magnetic coveringfilm structure is used, a current required to write data can be reduced,and data can be written with a low power consumption and a smallcurrent.

The structure of the concrete example has an advantage over a structureaccording to a fourth concrete example (will be described later) withrespect to the number of steps of etching, the number of masks, andmanufacturing cost.

Fourth Concrete Example

A constitution of a fourth concrete example of a memory cell used in amagnetic memory according to the present invention is shown in FIG. 12.The memory cell 3 according to the concrete example has a simple matrixarchitecture structure which uses a MOS transistor on only theperipheral portion of a memory array and which does not use selectivetransistors bit by bit. The memory cell 3 comprises a magneto-resistiveeffect element 2 according to the first embodiment, an underlying layer10 formed on the lower surface of a magnetization free layer 8 of themagneto-resistive effect element 2, a diode 15, a bit line 20electrically connected to the underlying layer 10 through the diode 15,a pair of word lines 30 ₁ and 30 ₂ formed on the side of themagnetization free layer through an insulating film, a conductive layer12 connected to the upper surface of the magneto-resistive effectelement 2, and a bit line 22. A magnetic covering film 25 is formed onthe bit line 20, and magnetic covering films 35 ₁ and 35 ₂ are formed onthe word lines 30 ₁ and 30 ₂, respectively.

In the fourth concrete example, data is read by turning on a MOStransistor connected to the bit line 20 and the bit line 5 to flow asense current in the magneto-resistive effect element 2. In a memorycell of a type which does not use a diode as in the first or secondconcrete example, in a read operation, a transistor connected to anotherbit line is opened, or the voltages of the bit line 20 and the bit line5 are made constant to reduce a current flowing around a non-selectedmagneto-resistive effect element as much as possible. However,disadvantageously, the current cannot be exactly zero. However, as inthe concrete example, the diode 15 is interposed between the underlyinglayer 10 and the bit line 20, so that the problem can be solved. As inthe first and second concrete examples, data is written by usingorthogonal bit lines 20 and the pair of word lines 30 ₁ and 30 ₂.Opposite current pulses are applied to the two word lines 30 ₁ and 30 ₂,respectively. At this time, the end portions of the two word lines 30 ₁and 30 ₂ are electrically connected to the end portion of the memoryarray block to make it possible that the current pulses are applied tothe word lines 30 ₁ and 30 ₂ by one driver and one sinker, so thatmemory array efficiency can be improved. The magnetic covering films 25,35 ₁ and 35 ₂ are applied to the bit line 20 and the word lines 30 ₁ and30 ₂ which are used to write data as described above. When the magneticcovering film structure is used, a current required to write data can bereduced, and data can be written with a low power consumption and asmall current.

A constitution of the magnetic memory according to the ninth embodimentis shown in FIG. 13. The magnetic memory according to the embodimentcomprises a plurality of memory cells 3 arranged in the form of anarray. Each memory cell 3 has a configuration obtained by replacing thebit line 20 with an underlying electrode 40 and arranging a word line33, a connection section 50, and a selective transistor 60.

A magnetic covering film 36 is formed on the word line 33. Theconnection section 50 has connection plugs 52, 54, and 56. Since theconnection plug 52 is formed as the same layer as that of the word line33, a magnetic covering film 53 is formed on the connection plug 52 likethe word line 33. The underlying electrode 40 is only used to read dataas will be described later, and is not used to write data. For thisreason, a magnetic covering film is not formed on the underlyingelectrode 40. The selective transistor 60 has a gate 62, a drain 64, anda source 66. One end of the connection section 50 connected to theunderlying electrode 40, and the other end is connected to the drain 64of the selective transistor 60.

In the magnetic memory according to this embodiment, data is read byturning on the selective transistor 60 to flow a sense current in theword line 22 through the magneto-resistive effect element 2. Data iswritten by using the word lines 30 ₁ and 30 ₂ and the word line 33parallel to the word lines 30 ₁ and 30 ₂. A magnetic covering film isapplied to the word lines 30 ₁ and 30 ₂ and the word line 33, asdescribed above. When the magnetic covering film structure is used, acurrent required to write data can be reduced, and data can be writtenwith a low power consumption and a small current.

In order to realize a further very-large capacity memory, amulti-layered structure is desirably obtained by using an architecturein which memory arrays can be laminated. For example, as shown in FIG.14, a multi-layered structure can be formed by forming a drawingelectrode 14, a connection section 16, and a memory cell 3 a between theconductive layer 12 and the word line 22 of the memory cell 3 accordingto this embodiment. The memory cell 3 a has the same constitution asthat of the memory cell 3. The memory cell 3 a comprises an underlyingelectrode 40 a connected to the connection section 16, an underlyinglayer 10 a formed on the underlying electrode 40 a, a magnetization freelayer 8 a formed on the underlying layer 10 a, a tunnel barrier layer 6a formed on the magnetization free layer 8 a, a magnetization-pinnedlayer 4 a formed on the tunnel barrier layer 6 a, an anti-ferromagneticlayer 9 a formed to cover the side surface and the upper surface of themagnetization-pinned layer 4 a, a conductive layer 12 a formed on theanti-ferromagnetic layer 9 a, and a pair of word lines 30 a ₁ and 30 a₂. In this manner, only the periphery of the magneto-resistive effectelement is laminated to make it possible to achieve a large-capacitymemory cell.

The memory cells shown in FIGS. 9 to 12 can be easily laminated byrepeating the structures of the memory cells as shown in FIG. 14.

Tenth Embodiment

A method of manufacturing a magnetic memory according to the tenthembodiment of the present invention will be described below withreference to FIGS. 15 to 27. This embodiment is a method ofmanufacturing a magnetic memory having a memory cell structure havingone transistor and one magneto-resistive effect element shown in FIG.13.

It is assumed that a selective transistor 60, a connection section 50,and a word line 33 shown in FIG. 13 are formed on a substrate. On aninsulating film 70 in which a tungsten via 51 connected to a connectionplug 52 of the connection section 50 is formed, an underlying electrodelayer 40 consisting of Ta (see FIG. 15). Subsequently, a layerconsisting of a metal (using Pt in this embodiment) which is not easilyetched by RIE (Reactive Ion Etching) is formed on the underlyingelectrode layer 40. Thereafter, a layer consisting of Pt is patterned toform a Pt layer 10 a on the word line 33 (see FIG. 16). The underlyingelectrode layer 40 consisting of Ta is patterned to form an underlyingelectrode 40 (see FIG. 16).

As shown in FIG. 16, an SiOx film 72 is formed and flattened by CMP(Chemical Mechanical Polishing), and a laminated film consisting ofNiFe/Ta/AlCu/Ta/NiFe is formed. A resist pattern (not shown) is formed.The laminated film consisting of NiFe/Ta/AlCu/Ta/NiFe is patterned byusing the resist pattern as a mask to form a word line forming film.Subsequently, the resultant structure is sputtered to form an NiFe filmon the side surface of a word line forming film 30, and the resistpattern is peeled to form the word line forming film 30 and a magneticcovering film 35 covering the word line forming film 30 (see FIG. 16).More specifically, the word line forming film 30 consists of Ta/AlCu/Ta,and the magnetic covering film 35 consists of NiFe.

An SiOx film 74 is formed on the entire surface of the substrate (seeFIG. 17). Thereafter, the SiOx film 74 is flattened by using CMP(Chemical Mechanical Polishing) to form a flattened SiOx film 74 a (seeFIG. 18). Subsequently, an SiNx film 76 is formed on the SiOx film 74 ato coat and develop the resist, thereby a resist pattern 78 having anopening 78 a on the word line 33, i.e., at the almost center of the wordline forming film 30 (see FIG. 18).

The SiNx film 76 is patterned by using an RIE method by using the resistpattern 78 as a mask, and the resist pattern 78 is removed. By using thepatterned SiNx film 76 as a mask, the SiOx film 74 a, the word lineforming films 30 and 35, and the SiOx film 72 are etched by using theRIE method to form an opening 80 (see FIG. 19) on the Pt layer 10 a.This etching, as shown in FIG. 19, is stopped to the Pt layer 10 a. Theopening 80 is formed to divide the word line forming film 30 into a pairof word lines 30 ₁ and 30 ₂. The opening 80 has an inverted-tapersection which is widened toward the bottom surface. However, the sectionis not shown in FIG. 19.

As shown in FIG. 20, an SiOx film 82 is deposited by using a CVD(Chemical Vapor Deposition) method. Since the SiOx film 82 is depositedby the CVD method, the SiOx film 82 is formed on not only the bottom ofthe opening 80 having the inverted-taper section but also the side.Thereafter, a milling apparatus having good directivity is used toremove the SiOx on the SiNx film 76 and the SiOx on the bottom of theopening 80, thereby leaving the SiOx film 82 on only the side of theopening 80 (see FIG. 21).

A Ti layer 10 b having a thickness of 10 nm, a Co—Cr—Pt layer 84 havinga thickness of 80 nm, an AlOx layer 86 serving as a tunnel barrier layerand having a thickness of 1.5 nm, and a Co—Cr—Pt layer 88 having athickness of 100 nm are formed (see FIG. 22). Since the opening 80 hasan inverted-taper section, the Ti layer 10 b, the Co—Cr—Pt layer 84, theAlOx layer 86, and the Co—Cr—Pt layer 88 are not laminated along theside of the opening 80, i.e., the side of the SiOx film 82, and arelaminated along only the direction of the film thickness as shown inFIG. 22.

CMP is performed to expose the SiOx film 72 (see FIG. 23). In thismanner, the Ti layer 10 b in the opening 80 constitutes the underlyinglayer 10 together with the Pt layer 10 a. The Co—Cr—Pt layer 84 and theAlOx layer 86 in the opening 80 serve as the magnetization free layer 8and the tunnel barrier layer 6, and the Co—Cr—Pt layer 88 is partiallyleft on the tunnel barrier layer 6.

Milling is performed to the resultant structure to slightly etch thesurface of the structure. Thereafter, as shown in FIG. 24, a Co—Cr—Ptlayer having a thickness of 100 nm and an Ir—Mn layer having a thicknessof 20 nm are formed and patterned to form a magnetization-pinned layer 4and to leave an Ir—Mn layer on the side surfaces of themagnetization-pinned layer 4. Thereafter, an Ir—Mn film is formed, andan Ir—Mn film is formed on the side surface of the magnetization-pinnedlayer 4. The Ir—Mn adhering a portion except for themagnetization-pinned layer 4 is etched by a milling apparatus havinggood directivity, and an anti-ferromagnetic film 9 consisting of Ir—Mnand covering the side surfaces and the upper surface of themagnetization-pinned layer 4 is formed (see FIG. 24).

An SiOx film 92 is deposited on the entire surface (see FIG. 25).Thereafter, the SiOx film 92 is flattened by using CMP to form aflattened SiOx film 92 a.

A via hole connecting with the anti-ferromagnetic film 9 on the uppersurface of the magnetization-pinned layer 4 is formed in the flattenedSiOx film 92 a, and W (tungsten) is buried in the via hole to form aconductive layer 12. Subsequently, the resultant structure is subjectedto CMP, and Ti/AlCu/Ti films are sequentially formed and patterned toform a word line 22 connected to the conductive layer 12 (see FIG. 27).

In this manner, a magnetic memory is manufactured by the manufacturingmethod according to the embodiment. As a comparative example, a magneticmemory which was manufactured by the manufacturing method of theembodiment except that an anti-ferromagnetic film consisting of Ir—Mn isformed on the side surface of the magnetization-pinned layer 4 wasformed.

In both the magnetic memory of the embodiment and the magnetic memory ofthe comparative example, an in-plane aspect ratio of TMR elements wasset at 1:1, and a size was set at 0.4 μm×0.4 μm. An AlOx film 6 wasformed such that an Al film was formed and then subjected to plasmaoxidation.

Thereafter, in both the magnetic memory of the embodiment and themagnetic memory of the comparative example, a magnetic field was appliedin a direction perpendicular to the film surface, and annealing wasperformed while applying the perpendicular magnetic field.

With respect to the magnetic memory of the embodiment and the magneticmemory of the comparative example, dependence of coercive force on thewidth of a write pulse magnetic field applied to the word lines 30 ₁ and30 ₂ shown in FIG. 13 was measured, Ku·V/(K·T) was evaluated on thebasis of Sharrock's equation (IEEE Trans. Magn. 26, 193 (1990). In thiscase, reference symbol Ku denotes an uniaxial magnetic anisotropyconstant of the magnetization free layer 8 serving as a magneticrecording layer; V denotes the volume of the magnetization free layer 8;K denotes Boltzmann constant; and T denotes an absolute temperature.

In the magnetic memory of the embodiment and the magnetic memory of thecomparative example, the volume V of the magnetization free layer 8 wasgiven by 0.4 μm×0.4 μm×80 nm. However, the value of Ku·V/(K·T) waslarge, i.e., 3760. Even though the volume V was set at 0.09 μm×0.09μm×80 nm, the value of Ku·V/(K·T) was considerably large, i.e., over180. It was apparent that the magnetic memory had a tolerance to heatdisturbances.

By using the structure of the embodiment, the recording layer having afilm thickness of 80 nm can be easily formed while holding themagnetization of the magnetic recording layer perpendicular, and a heatdisturbance stability parameter can be easily made large.

The magnetic memory of the embodiment and the magnetic memory of thecomparative example were subjected to a reliability test of rewritablecount resistance. The results are shown in FIG. 28. As is apparent fromFIG. 28, in the magnetic memory of the embodiment, an MR ratio did notdecrease even though data was written 10⁹ times. However, in thecomparative example in which no anti-ferromagnetic film is formed on theside surfaces of the magnetization-pinned layer, an MR ratio decreased,and preferable characteristics cannot be achieved as the characteristicsof the memory element.

As described above, in the magnetic memory of the embodiment, resistanceto data storage and data write can be confirmed, and preferablecharacteristics can be achieved as the characteristics of a nonvolatilemagnetic memory.

Eleventh Embodiment

A magnetic memory according to an eleventh embodiment of the presentinvention will be described below. The magnetic memory manufactured by amanufacturing method according to the embodiment has a configurationobtained by replacing a magneto-resistive effect element of the magneticmemory manufactured by the manufacturing method of the tenth embodimentshown in FIGS. 15 to 27 with the magneto-resistive effect element shownin FIG. 6.

Therefore, the steps in manufacturing the magnetic memory of theembodiment are almost the same as the manufacturing steps of the tenthembodiment. However, in the magnetic memory of the eleventh embodiment,as shown in FIG. 6, the anti-ferromagnetic film 9 is not formed on themagnetization-pinned layer 4 constituted by the magnetization-pinnedlayer 4 a, the nonmagnetic conductive layer 4 b, and the hard bias layer4 c. For this reason, in the steps of forming the magnetization-pinnedlayer 4 and the anti-ferromagnetic film 9 shown in FIG. 24 of the tenthembodiment, the magnetization-pinned layer 4 a, the nonmagneticconductive layer 4 b, and the hard bias layer 4 c are formed (withoutforming an Ir—Mn film) in place of the magnetization-pinned layer 4 andthe anti-ferromagnetic film 9 and patterned. Thereafter, an Ir—Mn filmis formed. The resultant structure is milled with good directivity tophysically remove the Ir—Mn layer on the upper side of themagnetization-pinned layer 4 constituted by the magnetization-pinnedlayer 4 a, the nonmagnetic conductive layer 4 b, and the hard bias layer4 c and the Ir—Mn layer on the SiNx film 76. The following steps areperformed by the same manner as that of the tenth embodiment.

The structure of the TMR element manufactured in the embodiment includesa magnetization free layer 8 consisting of Fe—Pt and a thickness of 100nm, a tunnel barrier layer 6 consisting of AlOx and having a thicknessof 1.5 nm, a perpendicular magnetization layer 4 a consisting of Fe—Ptand having a thickness of 100 nm, a conductive layer 4 b consisting ofCu, and a hard bias layer 4 c consisting of Co—Pt—Cr and having athickness of 100 nm. As a film forming condition, a temperature duringformation of an Fe—Pt film was set at 300° C. For the sake ofcomparison, a magnetic memory in which an Ir—Mn film was not formed onthe side surface of the magnetization-pinned layer 4 was also formed.

In the magnetic memory of the embodiment and the magnetic memory of thecomparative example, magnetic fields were applied in directionsperpendicular to the film surfaces to perform annealing in the magneticfields.

With respect to the magnetic memory of the embodiment and the magneticmemory of the comparative example, dependence of coercive force on thewidth of a write pulse magnetic field applied to the word lines 30 ₁,and 30 ₂ shown in FIG. 13 was measured, Ku·V/(K·T) was evaluated on thebasis of Sharrock's equation (IEEE Trans. Magn. 26, 193 (1990). In thiscase, reference symbol Ku denotes an uniaxial magnetic anisotropyconstant of the magnetization free layer 8 serving as a magneticrecording layer; V denotes the volume of the magnetization free layer 8;K denotes Boltzmann constant; and T denotes an absolute temperature.

In the magnetic memory of the embodiment and the magnetic memory of thecomparative example, the volume V of the magnetization free layer 8 wasgiven by 0.4 μm×0.4 μm×80 nm. However, the value of Ku·V/(K·T) waslarge, i.e., 4700. Even though the volume V was set at 0.09 μm×0.09μm×80nm, the value of Ku·V/(K·T) was considerably large, i.e., over 320.It was apparent that the magnetic memory had a tolerance to heatdisturbances.

By using the structure of the embodiment, the recording layer having afilm thickness of 100 nm can be easily formed while holding themagnetization of the magnetic recording layer perpendicular, and a heatdisturbance stability parameter can be easily made large.

The magnetic memory of the embodiment and the magnetic memory of thecomparative example were subjected to a reliability test of rewritablecount resistance. The results are shown in FIG. 29. As is apparent fromFIG. 29, in the magnetic memory of the embodiment, an MR ratio did notdecrease even though data was written 10⁹ times. However, in thecomparative example in which no anti-ferromagnetic film is formed on theside surfaces of the magnetization-pinned layer, an MR ratio decreased,and preferable characteristics cannot be achieved as the characteristicsof the memory element.

As described above, in the magnetic memory of the embodiment, resistanceto data storage and data write can be confirmed, and preferablecharacteristics can be achieved as the characteristics of a nonvolatilemagnetic memory.

Twelfth Embodiment

A magnetic memory according to a twelfth embodiment of the presentinvention will be described below with reference to FIG. 30. FIG. 30 isa sectional view showing the configuration of the magnetic memoryaccording to the embodiment. The magnetic memory according to theembodiment has a configuration obtained by removing the word lines 30 ₁,30 ₂, and 33 and magnetic covering films 35 ₁, 35 ₂, and 36 coveringthese word lines in the magnetic memory according to the ninthembodiment shown in FIG. 13. In the magnetic memory according to theembodiment, information is written in a magnetization free layer 8serving as a magnetic recording layer by a spin injection method. Thewrite principle of the spin injection method is as follows.

a) Writing operation of spin inversion obtained by changing the spinmoments of the magnetization-pinned layer 4 and the magnetic recordinglayer 8 from antiparallel to parallel is performed by flowing a currentfrom the underlying electrode 40 to the word line 22 through themagneto-resistive effect element 2. More specifically, a current flowsfrom the magnetic recording layer 8 to the magnetization-pinned layer 4in the magneto-resistive effect element 2. When electrons are injectedfrom the magnetization-pinned layer 4 into the magnetic recording layer8, electrons spin-polarized by the magnetization-pinned layer 4 tunnelthe tunnel barrier layer 6 to generate spin torque in the magneticrecording layer 8, and the spin of the magnetic recording layer 8 isinverted from antiparallel to parallel.

b) Writing operation of spin inversion obtained by changing the spinmoments of the magnetization-pinned layer 4 and the magnetic recordinglayer 8 from parallel to antiparallel is performed by flowing a currentfrom the word line 22 to the underlying electrode 40 through themagneto-resistive effect element 2. More specifically, a current flowsfrom the magnetization-pinned layer 4 to the magnetic recording layer 8in the magneto-resistive effect element 2. When electrons are injectedfrom the magnetic recording layer 8 into the magnetization-pinned layer4, electrons spin-polarized by the magnetic recording layer 8 tunnel thetunnel barrier layer 6. At this time, electrons having the same spindirection as the spin direction of the magnetization-pinned layer 4 havehigh tunnel probabilities and easily tunnel the tunnel barrier layer 6.However, electrons having antiparallel spin are reflected. The electronsreflected to the magnetic recording layer 8 generate spin torque in themagnetic recording layer 8, and the spin of the magnetic recording layer8 is inverted from parallel to antiparallel.

A manufacturing procedure of a magnetic memory according to theembodiment is as follows.

An insulating interlayer is deposited on a substrate on which theselective transistor 60 is formed. An opening is formed in theinsulating interlayer. The opening is buried with W (tungsten) to form aburied connection section 50. An underlying electrode 40 consisting ofTa is formed to be connected to the connection section. Thereafter, onthe underlying electrode 40, an underlying layer 10 consisting of Ti andhaving a thickness of 10 nm, a magnetic recording layer 8 consisting ofCo—Cr—Pt and having a thickness of 80 nm, a tunnel barrier layerconsisting of AlOx and having a thickness of 1.0 nm, amagnetization-pinned layer 4 consisting of Co—Cr—Pt and having athickness of 100 nm, an anti-ferromagnetic layer consisting of Ir—Mn andhaving a thickness of 20 nm, and a conductive layer 12 obtained bylaminating an Ru layer having a thickness of 15 nm and a Ta layer havinga thickness of 120 nm are formed. Thereafter, slimming of a resist (notshown) is performed at 140° for 10 minutes to form a resist pattern fora TMR element. As the resist pattern for the TMR element, a patternhaving a size of 0.08 μm×0.14 μm is manufactured. By using the resistpattern as a mask, the conductive layer 12 having a laminated structureconsisting of Ta and Ru is patterned by RIE. Thereafter, by using thepatterned conductive layer 12 as a mask, a TMR film constituted by a Tilayer, a Co—Cr—Pt layer, an AlOx layer, a Co—Cr—Pt layer, and an Ir—Mnlayer is patterned by milling up to the tunnel barrier layer 6consisting of AlOx.

Thereafter, an anti-ferromagnetic film consisting of Ir—Mn is depositedand subjected to milling in a direction perpendicular to the filmsurface, so that the anti-ferromagnetic film 9 is formed on the side ofthe magnetization-pinned layer 4. Subsequently, a protective filmconsisting of an SiOx is formed, and the underlying electrode 40consisting of Ta is etched by RIE. Thereafter, an insulating interlayer(not shown) consisting of SiOx is deposited and etched back to exposethe Ta layer of the conductive layer 12. Subsequently, after contactcleaning of the exposed Ta layer is performed, a word line 22 connectedto the Ta layer is formed, thereby manufacturing the magnetic memoryaccording to the embodiment. Thereafter, a magnetic field is applied inthe direction perpendicular to the film surface to perform annealing inthe magnetic field.

With respect to the magnetic memory of the embodiment manufactured bythe manufacturing method, dependence of coercive force on a sweep rateof a magnetic field was measured, Ku·V/(K·T) was evaluated on the basisof Sharrock's equation (IEEE Trans. Magn. 26, 193 (1990). In this case,reference symbol Ku denotes an uniaxial magnetic anisotropy constant ofthe magnetization free layer 8 serving as a magnetic recording layer; Vdenotes the volume of the magnetization free layer 8; K denotesBoltzmann constant; and T denotes an absolute temperature.

In the magnetic memory of the embodiment, the value of Ku·V/(K·T) was320. Even though the volume V of the magnetization free layer 8 was setat 0.09 μm×0.09 μm×80 nm, the value of Ku·V/(K·T) was considerablylarge, i.e., over 180. It was apparent that the magnetic memory had atolerance to heat disturbances. By using the structure of theembodiment, the recording layer having a film thickness of 80 nm can beeasily formed while holding the magnetization of the magnetic recordinglayer perpendicular, and a heat disturbance stability parameter can beeasily made large.

A result obtained by measuring spin injection writing operation is shownin FIG. 31. As is apparent from FIG. 31, spin injection writingoperation can be performed by changing the direction of a current.

As described above, in the magnetic memory according to the embodiment,resistance to data storage and data write can be confirmed, andpreferable characteristics can be achieved as the characteristics of anonvolatile magnetic memory.

Each of the magnetic memories according to the ninth to twelfthembodiments further comprises a sense current control device circuitwhich controls a sense current to be flowed in the magneto-resistiveeffect element to read information stored in the magneto-resistiveeffect element, a circuit to apply a write pulse, and a driver.

In each of the embodiments, a tunnel barrier layer is used as anonmagnetic layer between a magnetization-pinned layer and a magneticrecording layer of the magneto-resistive effect element. However, whenthe area of the magneto-resistive effect element is 300 nm² or less, asthe material of the nonmagnetic layer, a nonmagnetic metal (for example,Cu, Cu alloy, or a mixture of Cu and a dielectric material (e.g., SiO₂,SiN, Al₂O₃, or the like)) can be used.

The embodiments of the present invention have been described withreference to the concrete examples. However, the present invention isnot limited to the concrete examples. For example, the following isincluded in the spirit and scope of the present invention. That is, aperson skilled in the art appropriately selects concrete materials of aferromagnetic layer, an insulating film, an anti-ferromagnetic layer, anonmagnetic metal layer, an electrode, and the like which constitute amagneto-resistive effect element, film thicknesses, shapes, and sizes toexecute the present invention as described above, so that the sameadvantages as described above can be obtained.

Similarly, the following is also included in the spirit and scope of thepresent invention. That is, a. person skilled in the art appropriatelyselects structures, materials, shapes, and sizes of elementsconstituting a magnetic memory according to the present invention toexecute the present invention as described above, so that the sameadvantages as described above can be obtained.

According to the present invention, the magneto-resistive effect elementof this patent is similarly applied to not only a magnetic head of alongitudinal magnetic recording scheme but also a magnetic head of aperpendicular magnetic recording scheme or a magnetic reproducingdevice, so that the advantages as described above can be obtained.

In addition, all magnetic memories which can be executed such thatdesigns are appropriately changed by a person skilled in the art on thebasis of the magnetic memory as the embodiment of the present inventionare also included in the spirit and scope of the invention.

As described above, according to the present invention, excellentthermal stability can be achieved even though the magneto-resistiveeffect element is micropatterned, and stable magnetic domains of themagnetization-pinned layer can be kept even though switching of spinmoments of the magnetization free layer is repeated.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcepts as defined by the appended claims and their equivalents.

1. A magneto-resistive effect element comprising: a magnetization-pinned layer including a magnetic film having a first surface, a second surface opposite to the first surface, and third surfaces different from the first and second surfaces, the magnetic film having a spin moment oriented in a direction perpendicular to the first surface and pinned in the direction; a magnetic recording layer provided to face the first surface and having a spin moment oriented in a direction perpendicular to the first surface, a direction of the spin moment of the magnetic recording layer being parallel or antiparallel to that of the magnetization-pinned layer; a nonmagnetic layer formed between the magnetization-pinned layer and the magnetic recording layer; and an anti-ferromagnetic film formed on at least the third surfaces of the magnetization-pinned layer.
 2. The magneto-resistive effect element according to claim 1, wherein the nonmagnetic layer is a tunnel barrier layer.
 3. The magneto-resistive effect element according to claim 1, further comprising a nonmagnetic conductive layer formed on the second surface of the magnetic film.
 4. The magneto-resistive effect element according to claim 1, wherein the magnetization-pinned layer further comprises a nonmagnetic conductive layer formed on the second surface of the magnetic film and a bias-applying magnetic layer formed on a surface of the nonmagnetic conductive layer opposite to the magnetic film.
 5. The magneto-resistive effect element according to claim 1, wherein the anti-ferromagnetic film is also formed on the second surface of the magnetic film.
 6. The magneto-resistive effect element according to claim 1, wherein the magnetic film of the magnetization-pinned layer is any one of a layer containing any one selected from the groups of Co, Fe, Ni, an alloy thereof, Co—Cr—Pt—Ta, Co—Cr—Nb—Pt, Co—Cr—Pt, Co—Pt—Cr—O, Co—Cr—Pt—SiO₂, Co—Cr—Pt—B, Fe—Pt, Tb—Fe—Co, and Pr—Tb—Co, a multi-layered film obtained by laminating layers consisting of Co—Cr—Pt and Ti, a multi-layered film obtained by laminating layers consisting of Co—Cr—Ta, Co—Zr—Nb, and Co—Sm, a multi-layered film obtained by laminating layers consisting of Co—Cr—Ta and Pt, a multi-layered film obtained by laminating layers consisting of Co and Pd, and a multi-layered film obtained by laminating layers consisting of Co—B and Pd.
 7. The magneto-resistive effect element according to claim 1, wherein the magnetic recording layer is any one of a layer containing any one selected from the groups of Co—Cr—Pt—Ta, Co—Cr—Nb—Pt, Co—Cr—Pt, Co—Pt—Cr—O, Co—Cr—Pt—SiO₂, Co—Cr—Pt—B, Fe—Pt, Tb—Fe—Co, and Pr—Tb—Co, a multi-layered film obtained by laminating layers consisting of Co—Cr—Pt and Ti, a multi-layered film obtained by laminating layers consisting of Co—Cr—Ta, Co—Zr—Nb, and Co—Sm, a multi-layered film obtained by laminating layers consisting of Co—Cr—Ta and Pt, a multi-layered film obtained by laminating layers consisting of Co and Pd, and a multi-layered film obtained by laminating layers consisting of Co—B and Pd.
 8. The magneto-resistive effect element according to claim 1, wherein the nonmagnetic layer is formed of nonmagnetic metal. 